Apple has pushed out a new carrier update, but with very little detail. It …

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If you've seen the recent carrier update message in iTunes that has popped up over the last few days, you might wonder exactly what that update brings. After all, Apple fails to mention what "carrier settings" will be updated and how it might affect your iPhone. For me, I saw it just as I inserted my no-plan, out-of-contract iPhone into its dock. Was Apple gunning for me? Trying to make me run the phone with a plan? Er, no.

It turns out that the carrier settings update is little more than a bunch of localized strings files and a half dozen images. I read through the Apple KB post about the update and located the ATT_US.ipcc file. It's located in Library/iTunes/iPhone Carrier Support/ in my user folder.

Guessing that the file was, typical for Apple, a renamed zip, I unzipped the ipcc and took a peek inside. Sure enough, it unzipped to standard Payload folder just like the iPhone Apps do. There was a bundle inside called ATT_US. This offered a series of localized lproj subfolders with property lists and, strings files, and images.

The images are, as expected, iPhone-coded PNG. To convert to a visible format, I used iPhonePNG, one of the many cute little converter utilities available to make a phone PNG viewable on the Mac. As you can see, the PNGs refer to AT&T's upcoming MicroCell service. FSO_ images are used by SpringBoard to display the carrier in the 20-pixel high status line at the top of the iPhone. Each image has a white version and a black version; these two form factors are used for when the status line is dark or light to provide a contrast on the display and are stored on the phone in the SpringBoard application in the CoreServices folder.

The update also offers carrier services strings. These are the items that appear in Settings > Phone > [Carrier Name] Services. They provide the GSM codes that let you check your bill, access directory assistance, and so forth, and are essentially unchanged from the current AT&T services list on my phone. Which, by the way, apply only to prepaid accounts. As a post-paid customer, the shortcuts shown on this screen do not all work. For me, I use *777# to check my account balance, not *225#.

As for the last piece of the puzzle, locversion.plist property lists scattered about, they merely update the version/revision level to the latest carrier update settings.

So, when all is said and done, it turns out that the whole carrier update thing is just a little bookkeeping. It won't do any harm to your out-of-service iPhone. (Mine continues to work just fine.) And it isn't doing anything nefarious or underhanded.

Hat-tip to TUAW, whose excellent write-up Jacqui pointed me to as I was exploring all this. I was not, however, able to confirm anything in this update regarding the Saudi Arabian Mobily network or the Emerati Etisalat network as mentioned in the TUAW post. I used some command-line grepping to look for those services (see below) and came up empty handed. If you know any more details about any hints in the update regarding these carriers, drop a note in the comments. Thanks!